The present invention is directed to phase change (hot melt) ink compositions. More specifically, the present invention is directed to phase change ink compositions suitable for use in ink jet printing processes. One embodiment of the present invention is directed to a phase change ink composition comprising an ink vehicle, a colorant, and a nonpolymeric organic gelator selected from the group consisting of anthracene-based compounds, steroid compounds, partially fluorinated high molecular weight alkanes, high molecular weight alkanes with exactly one hetero atom, chiral tartrate compounds, chiral butenolide-based compounds, bis-urea compounds, guanines, barbiturates, oxamide compounds, ureidopyrimidone compounds, and mixtures thereof, said organic gelator being present in the ink in an amount of no more than about 20 percent by weight of the ink, said ink having a melting point at or below which the ink is a solid, said ink having a gel point at or above which the ink is a liquid, and said ink exhibiting a gel state between the melting point and the gel point, said ink exhibiting reversible transitions between the solid state and the gel state upon heating and cooling, said ink exhibiting reversible transitions between the gel state and the liquid state upon heating and cooling, said melting point being greater than about 35° C., said gel point being greater than said melting point.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing, as disclosed in, for example, U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE 4205713AL, the disclosures of each of which are totally incorporated herein by reference.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. In a specific embodiment, a series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye or a mixture of dyes. For example, magenta can be obtained by using a mixture of Solvent Red Dyes or a composite black can be obtained by mixing several dyes. U.S. Pat. No. 4,889,560, U.S. Pat. No. 4,889,761, and U.S. Pat. No. 5,372,852, the disclosures of each of which are totally incorporated herein by reference, teach that the subtractive primary colorants employed can comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, and Basic Dyes. The colorants can also include pigments, as disclosed in, for example, U.S. Pat. No. 5,221,335, the disclosure of which is totally incorporated herein by reference. U.S. Pat. No. 5,621,022, the disclosure of which is totally incorporated herein by reference, discloses the use of a specific class of polymeric dyes in phase change ink compositions.
Phase change inks have also been used for applications such as postal marking and industrial marking and labelling.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
Compositions suitable for use as phase change ink carrier compositions are known. Some representative examples of references disclosing such materials include U.S. Pat. No. 3,653,932, U.S. Pat. No. 4,390,369, U.S. Pat. No. 4,484,948, U.S. Pat. No. 4,684,956, U.S. Pat. No. 4,851,045, U.S. Pat. No. 4,889,560, U.S. Pat. No. 5,006,170, U.S. Pat. No. 5,151,120, U.S. Pat. No. 5,372,852, U.S. Pat. No. 5,496,879, European Patent Publication 0187352, European Patent Publication 0206286, German Patent Publication DE 4205636AL, German Patent Publication DE 4205713AL, and PCT Patent Application WO 94/04619, the disclosures of each of which are totally incorporated herein by reference. Suitable carrier materials can include paraffins, microcrystalline waxes, polyethylene waxes, ester waxes, fatty acids and other waxy materials, fatty amide containing materials, sulfonamide materials, resinous materials made from different natural sources (tall oil rosins and rosin esters, for example), and many synthetic resins, oligomers, polymers, and copolymers.
U.S. Pat. No. 5,006,170 (Schwarz et al.) and U.S. Pat. No. 5,122,187 (Schwarz et al.), the disclosures of each of which are totally incorporated herein by reference, disclose hot melt ink compositions suitable for ink jet printing which comprise a colorant, a binder, and a propellant selected from the group consisting of hydrazine; cyclic amines; ureas; carboxylic acids; sulfonic acids; aldehydes; ketones; hydrocarbons; esters; phenols; amides; imides; halocarbons; urethanes; ethers; sulfones; sulfamides; sulfonamides; phosphites; phosphonates; phosphates; alkyl sulfines; alkyl acetates; and sulfur dioxide. Also disclosed are hot melt ink compositions suitable for ink jet printing which comprise a colorant, a propellant, and a binder selected from the group consisting of rosin esters; polyamides; dimer acid amides; fatty acid amides; epoxy resins; fluid paraffin waxes; fluid microcrystalline waxes; Fischer-Tropsch waxes; polyvinyl alcohol resins; polyols; cellulose esters; cellulose ethers; polyvinyl pyridine resins; fatty acids; fatty acid esters; poly sulfonamides; benzoate esters; long chain alcohols; phthalate plasticizers; citrate plasticizers; maleate plasticizers; sulfones; polyvinyl pyrrolidinone copolymers; polyvinyl pyrrolidone/polyvinyl acetate copolymers; novalac resins; natural product waxes; mixtures of linear primary alcohols and linear long chain amides; and mixtures of linear primary alcohols and fatty acid amides. In one embodiment, the binder comprises a liquid crystalline material.
U.S. Pat. No. 5,021,802 (Allred), the disclosure of which is totally incorporated herein by reference, discloses impulse ink or bubble jet inks which comprise 90 to 99.9 percent by weight of aqueous sol-gel medium and 0.1 to 10 percent by weight colorant. The inks are thermally reversible sol-gels which are gels at ambient temperatures and sols at temperatures between about 400 to 100° C.
U.S. Pat. No. 5,180,425 (Matrick et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink for ink jet printers which comprises an aqueous carrier medium, pigment dispersion or dye, and a polyol/alkylene oxide condensate cosolvent which eliminates film formation on thermal ink jet resistor surfaces thereby eliminating non-uniformity in optical density. The cosolvent present at least 5 percent has a solubility in water of at least 4.5 parts in 100 parts of water at 25° C. and a general formula: wherein X=—H or —CH3; R=—H, —CH3, —C2H5, —C3H7, —C4H9, or —CH2O(CH2CH2O)eH; b=0 or 1, a+d+f(c+e)=2 to 100; and f=1 to 6, the cosolvent being present in the amount of at least 4.5 percent based on the total weight of the ink jet ink composition. These inks exhibit freedom from thermal resistor film formation, have excellent decap performance, are storage stable and give images having excellent print quality.
U.S. Pat. No. 5,531,817 (Shields et al.), the disclosure of which is totally incorporated herein by reference, discloses the control of color bleed (the invasion of one color into another on the surface of the print medium) using ink-jet inks by employing either high molecular weight polymers that exhibit a reversible gelling nature with heat or certain amine oxide surfactants that undergo sol-gel transitions. The inks of the invention further include a vehicle and a dye. The vehicle typically comprises a low viscosity, high boiling point solvent and water. Certain high molecular weight polymers, under the correct solution conditions, can form gels which can be subsequently melted by heating of the gel. When the melted gel is cooled, it will then reform into a gel. The viscosity of an ink employing such a gel can be reduced to a viscosity low enough to permit jetting from the print cartridge. After leaving the print cartridge, the melted gel will again reform into a highly viscous gel to immobilize the droplet of ink and prevent its migration on the media. Therefore, two drops of different colors, when printed next to one another will thus be inhibited from migrating or bleeding into one another.
U.S. Pat. No. 5,476,540 (Shields et al.), the disclosure of which is totally incorporated herein by reference, discloses a method for controlling color bleed between adjacent multi-color ink regions on a print medium. Color bleed involves the migration of color agents between adjacent zones in a multicolored printed image on a print medium. A first composition containing a gel-forming species and a color agent is brought into contact on a region of the print medium with a second composition having a color agent and a gel-initiating species or chemical conditions which bring about gelation. In alternative embodiments, the print medium may be pretreated with either a gel-initiating species or a gel-forming species (with no colorant), followed by treatment with a gel-forming species or gel-initiating species (with colorant), respectively. The formation of the gel upon the print medium impedes the movement of the color agent or agents and thus reduces the color bleed between adjacent zones.
U.S. Pat. No. 5,389,958 (Bui et al.), the disclosure of which is totally incorporated herein by reference, discloses a method and apparatus whereby an intermediate transfer surface of a layer of sacrificial liquid is applied to a supporting surface and a phase change ink is deposited on the liquid layer. The inked image is then contact transferred to a final receiving substrate.
U.S. Pat. No. 5,554,212 (Bui et al.), the disclosure of which is totally incorporated herein by reference, discloses an aqueous phase change ink containing a water dispersible sulfonated polyester gloss agent and a selected concentration of hyperthermogelling component that causes the ink to gel when its temperature is increased to its thermo-inversion point or when the concentration of the hyperthermogelling component is increased by evaporation, or substrate absorption, of water from the ink. The ink may be jetted directly onto a heated and/or absorptive substrate or jetted onto a cooler and/or hydrophobic surface before being transferred to the substrate. The thermo-inversion point is preferably about ambient temperature, and the preferred hyperthermogelling component is a nonionic surfactant, such as an ethylene oxide propylene oxide block copolymer surfactant.
U.S. Pat. No. 5,462,591 (Karandikar et al.), the disclosure of which is totally incorporated herein by reference, discloses an aqueous phase change ink that contains a selected concentration of hyperthermogelling component that causes the ink to gel when its temperature is increased to its thermo-inversion point or when the concentration of the hyperthermogelling component is increased by evaporation, or substrate absorption, of water from the ink. The ink may be jetted directly onto a heated and/or absorptive substrate or jetted onto a cooler and/or hydrophobic surface before being transferred to the substrate. The thermo-inversion point is preferably about ambient temperature, and the preferred hyperthermogelling component is a nonionic surfactant, such as an ethylene oxide propylene oxide block copolymer surfactant.
U.S. Pat. No. 5,099,256 (Anderson), the disclosure of which is totally incorporated herein by reference, discloses an ink jet printer having a rotatable intermediate drum having a thermally conductive surface on which the ink droplets are printed from the printhead. The drum surface material is a suitable film forming silicone polymer having a high surface energy and surface roughness to prevent movement of the droplets after impact thereon. The printhead is located relative to the intermediate drum surface so that the ink droplets impact the drum surface with a large contact angle and the ink droplet image is transferred at a second location spaced from the printhead to minimize contaminating particles from the recording medium from reaching the printhead nozzles. The intermediate drum surface is heated to dehydrate the ink droplets prior to transfer from the intermediate drum to the recording medium. The silicone polymer coating enables substantially complete transfer of the dehydrated droplets to the recording medium, so that subsequent removal of the residual ink from the drum by a cleaning system is eliminated.
U.S. Pat. No. 4,538,156 (Durkee et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink jet printer utilizing a smooth surfaced transfer drum as an illustrative embodiment of the invention. The transfer drum and the print head assembly are mounted between a pair of side plates. A print head assembly, which comprises a number of ink jet nozzles, is also mounted between the side plates. The print head assembly is spaced apart from the drum and the nozzles thereof are spaced at equal distances along a line which is parallel to the axis of the drum. The print head assembly is movable in fine steps from left to right so that on successive rotations of the drum each nozzle is directed to a new track of a succession of tracks. After all tracks of the transfer drum have been served by a nozzle assembly, a printing medium, e.g., paper is brought in rolling contact with the drum to transfer the indicia on the drum to the printing medium while the print head assembly is returned to its starting position; and thereafter, if required, the drum is wiped clean in preparation for receiving the next page of information.
U.S. Pat. No. 5,761,597 (Smith et al.), the disclosure of which is totally incorporated herein by reference, discloses an improved fusing apparatus for fixing or fusing images on print media wherein a relatively small pressure applying surface, such as the surface of a rotatable pressure wheel, is lubricated with a lubricating medium such as silicone oil, and engages the printed image to apply pressure and fuse the image to the image receiving substrate. The fusing apparatus is mounted for reciprocal back and forth movement across the printed image on the image receiving substrate or medium to fuse the image into the substrate and flatten or smooth the upper exposed surface of the ink image. The pressure wheel is passed in multiple overlapping passes over the printed image to uniformly fuse the image into the media.
U.S. Pat. No. 5,195,430 (Rise), the disclosure of which is totally incorporated herein by reference, discloses a fixing and developing apparatus in which sheet material to be treated is passed through a high pressure nip defined by a pair of rollers. At least one of the rollers may have a composite construction. The composite roller includes an elongated tubular shell with a pressure applying external surface, an elongated core positioned within the tubular shell, and an elastomeric material disposed between the core and shell to support the shell on the core. The core may be of a number of configurations and may increase in transverse cross-sectional dimension from the respective ends of the core toward the center of the core. The core may taper continuously or in discrete steps from its center toward its first and second ends. In addition, the core may have a longitudinal cross-section with a crown in the shape of a beam deflection curve for a simply supported, uniformly constant cross-section beam. The shell may be similarly configured along its interior surface. Also, the elastomer may be compressed at the center of the roller relative to the ends of the roller to preload its center portion.
U.S. Pat. No. 4,889,761 (Titterington et al.), the disclosure of which is totally incorporated herein by reference, discloses a method for producing a light-transmissive phase change ink printed substrate which comprises providing a substrate, and then printing on at least one surface of the substrate a predetermined pattern of a light-transmissive phase change ink which initially transmits light in a non-rectilinear path. The pattern of solidified phase change ink is then reoriented to form an ink layer of substantially uniform thickness. This ink layer will, in turn, produce an image which then will transmit light in a substantially rectilinear path. In one aspect of the invention, the substrate is light transmissive, and the reoriented printed substrate exhibits a high degree of lightness and chroma, and transmits light in a substantially rectilinear path. In this way, the reoriented printed substrate can be used in a projection device to project an image containing clear, saturated colors.
U.S. Pat. No. 4,745,420 (Gerstenmaier), the disclosure of which is totally incorporated herein by reference, discloses a method of ejecting droplets of phase change or hot melt ink jet ink upon a target such as paper which includes a step of applying pressure to the droplets after they have cooled upon the paper in order to increase their coverage and, thus, minimize the volume of ink required to produce a high quality print with a high degree of resolution. Including a means for applying pressure to the cooled droplets, a suitable apparatus increases the area of the target covered by a particular droplet after spreading by at least five percent and preferably by twenty percent.
U.S. Pat. No. 6,320,018 (Sijbesma et al.), the disclosure of which is totally incorporated herein by reference, discloses a polymer comprising monomeric units linked via four H-bridges and bound within said polymer via a different bond. The bond via the H-bridges is much stronger than with known supramolecular polymers.
U.S. Pat. No. 5,892,116 (Weiss et al.) and PCT Patent Publication WO 97/24364 (Weiss et al.), the disclosures of each of which are totally incorporated herein by reference, disclose gelators that gel a variety of nonpolar and polar liquids. Moreover, gelation of various monomers with subsequent polymerization of the gelled monomers forms organic zeolites and membrane materials. An ionic gelator includes salts of compounds of formula (I)[R1R2R3X—R4]±Y±  Iwhere R1, R2, and R3 are the same or different hydrogen or organic groups including alkyl groups, alkenyl groups, alkynyl groups, aryl groups, arylalkyl groups, alkoxy groups, aryloxy groups; X is a Group IIIA or Group VA element; R4 is a steroidal group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an arylalkyl group, an alkoxy group, or an aryloxy group; and Y is a Group IA or Group VIIA element or one-half of a Group IIA or VIA element, that is, a divalent counterion. The gelling agent composition may include a single isomer or mixtures of isomers of the formula (I). A non-ionic gelator also includes compounds of the formula (II):R1R2R3X  IIwhere R1, R2, R3, and X are defined as above.
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While known compositions and processes are suitable for their intended purposes, a need remains for phase change inks that are suitable for hot melt ink jet printing processes, such as hot melt piezoelectric ink jet printing processes and the like. In addition, a need remains for phase change inks that can be jetted at lower temperatures than currently known phase change inks, thereby enabling reduced energy use and improved thermal stability of the ink. Further, a need remains for phase change inks that exhibit desirably low viscosity values at jetting temperatures, thereby enabling increased jetting frequency. Additionally, a need remains for phase change inks which generate images having a desirably low coefficient of friction, thereby improving performance when substrates having the inks printed thereon are passed through automatic document handlers in copiers and also improving feel of the image and in some cases improving dry smear characteristics. There is also a need for phase change inks that generate images with reduced pile height. In addition, there is a need for phase change inks that generate images with improved scratch resistance. Further, there is a need for phase change inks that generate images with improved look and feel characteristics. Additionally, there is a need for phase change inks that generate images with improved hardness and toughness characteristics. A need also remains for phase change inks that are suitable for high speed printing, thereby enabling transaction and production printing applications.